Does "hollow rim" = single walled?

I would think so, but I don't know for sure. They should specify between single and double walled rims unless there is no question imo, but in this case, they do not. So would a "hollow rim" mean a single walled rim?

If it is single-walled, there is no space to be "hollow", right?
On one side of the single wall is the air that you are currently breathing. On the other side of the single wall there are some spoke nipple heads, a rim strip, an inner tube...